CN113904650A - Bulk acoustic wave resonant structure and method of manufacturing the same - Google Patents
Bulk acoustic wave resonant structure and method of manufacturing the same Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
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- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02047—Treatment of substrates
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02086—Means for compensation or elimination of undesirable effects
- H03H9/02133—Means for compensation or elimination of undesirable effects of stress
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/0504—Holders; Supports for bulk acoustic wave devices
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/023—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
Abstract
The embodiment of the invention discloses a bulk acoustic wave resonance structure and a manufacturing method thereof, wherein the bulk acoustic wave resonance structure comprises: a substrate; the reflecting structure, the first electrode layer, the piezoelectric layer and the second electrode layer are sequentially stacked on the substrate; a support layer at least partially located above the piezoelectric layer, wherein part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer; a protective layer on the support layer; a first cavity is formed between the protective layer and the second electrode layer; and the projection overlapping area of the reflecting structure, the first electrode layer, the piezoelectric layer and the second electrode layer along the thickness direction of the substrate is an active area.
Description
Technical Field
The embodiment of the invention relates to the field of semiconductors, in particular to a bulk acoustic wave resonance structure and a manufacturing method thereof.
Background
Bulk Acoustic Wave (BAW) resonators (or "Bulk Acoustic Wave resonator structures") have the advantages of small size, high quality factor (Q value), and the like, and thus are widely used in mobile communication technologies, such as filters or duplexers in mobile terminals. In a mobile terminal, there is a case where a plurality of frequency bands are used simultaneously, which requires a steeper skirt and a smaller insertion loss of a filter or a duplexer. The performance of the filter is determined by the resonators that make up it, and increasing the Q of the resonators allows for steep skirts and small insertion loss. How to improve the Q value of the bulk acoustic wave resonator becomes an urgent problem to be solved.
Disclosure of Invention
In view of the above, embodiments of the present invention provide a bulk acoustic wave resonator structure and a method for manufacturing the same.
An embodiment of the present invention provides a bulk acoustic wave resonant structure, including:
a substrate;
the reflecting structure, the first electrode layer, the piezoelectric layer and the second electrode layer are sequentially stacked on the substrate;
a support layer at least partially located above the piezoelectric layer, wherein part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer;
a protective layer on the support layer; a first cavity is formed between the protective layer and the second electrode layer;
and the area where the reflection structure, the first electrode layer, the piezoelectric layer and the second electrode layer are projected and overlapped along the thickness direction of the substrate is an active area.
Another aspect of the embodiments of the present invention provides a method for manufacturing a bulk acoustic wave resonant structure, including:
sequentially forming a reflecting structure, a first electrode layer, a piezoelectric layer and a second electrode layer which are stacked on a substrate;
forming at least a portion of a support layer over the piezoelectric layer; wherein part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer;
forming a protective layer on the support layer; a first cavity is formed between the protective layer and the second electrode layer;
and the area where the reflection structure, the first electrode layer, the piezoelectric layer and the second electrode layer are projected and overlapped along the thickness direction of the substrate is an active area.
In the embodiment of the invention, a support layer is arranged on the piezoelectric layer, part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer, in addition, a protective layer is formed on the support layer, and a first cavity is formed between the protective layer and the second electrode layer. In this way, by arranging the support layer and the protective layer at the edge of the active region, the support layer can suppress transverse shear waves (lateral waves) generated when the bulk acoustic wave resonator is excited by an electric field, reduce energy loss of longitudinal waves, and improve the Q value. In addition, compared with the contact area between the supporting layer and the protective layer in the related art, the contact area between the supporting layer and the protective layer in the embodiment of the invention is increased, so that the combination of the supporting layer and the protective layer is firmer, and the reliability of the resonance structure is improved.
Drawings
Fig. 1 is a schematic diagram of a piezoelectric layer in a bulk acoustic wave resonator structure according to an embodiment of the present invention generating an acoustic wave due to a piezoelectric effect;
fig. 2 is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention;
fig. 3a is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention;
fig. 3b is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention;
fig. 3c is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention;
fig. 4 is a schematic cross-sectional view of a bulk acoustic wave resonator structure provided in the related art;
fig. 5 is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention;
FIG. 6 is a schematic cross-sectional view of a bulk acoustic wave resonator structure in which the support layer comprises a material according to an embodiment of the present invention;
FIG. 7 is a schematic cross-sectional view of a bulk acoustic wave resonator structure with a support layer comprising three materials according to an embodiment of the present invention;
FIG. 8 is a schematic top view of a discontinuous structure of a first supporting layer and a second supporting layer according to an embodiment of the present invention;
FIG. 9a is a schematic top view of a continuous structure of a first supporting layer and a second supporting layer according to an embodiment of the present invention;
FIG. 9b is a cross-sectional view of a continuous structure of a first support layer and a second support layer according to an embodiment of the present invention;
FIG. 9c is a cross-sectional view of a continuous structure of a first support layer and a second support layer according to an embodiment of the present invention;
fig. 10 is a schematic flow chart illustrating an implementation of a method for manufacturing a bulk acoustic wave resonant structure according to an embodiment of the present invention;
11a-11k are schematic diagrams illustrating implementation processes of a first bulk acoustic wave resonant structure manufacturing method according to an embodiment of the present invention;
12a-12d are schematic diagrams illustrating implementation processes of a second method for manufacturing a bulk acoustic wave resonant structure according to an embodiment of the present invention;
FIGS. 13a-13f are schematic diagrams illustrating an implementation process of a third method for manufacturing a bulk acoustic wave resonant structure according to an embodiment of the present invention;
14a-14f are schematic diagrams illustrating a fourth method for manufacturing a bulk acoustic wave resonant structure according to an embodiment of the present invention;
fig. 15a to 15c are schematic diagrams of three implementation manners for implementing the thickness change of the adjustment layer according to the embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be further elaborated with reference to the drawings and the embodiments. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The present invention is more particularly described in the following paragraphs with reference to the accompanying drawings by way of example. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
In the embodiment of the present invention, the term "a is connected to B" includes A, B where a is connected to B in contact with each other, or A, B where a is connected to B in a non-contact manner with other components interposed therebetween.
In the embodiments of the present invention, the terms "first", "second", and the like are used for distinguishing similar objects, and are not necessarily used for describing a particular order or sequence.
The technical means described in the embodiments of the present invention may be arbitrarily combined without conflict.
As shown in fig. 1, when electric energy is applied to upper and lower electrodes of a bulk acoustic wave resonator, piezoelectric layers located in the upper and lower electrodes generate an acoustic wave due to a piezoelectric effect. In addition to longitudinal waves, transverse shear waves (transverse shear waves may also be referred to as lateral waves or shear waves) are generated within the piezoelectric layer. The presence of transverse shear waves affects the energy of the primary longitudinal wave, which results in loss of energy and formation of parasitic resonances (spurious modes) that degrade the Q-value of the bulk acoustic wave resonator.
Therefore, one method to improve the Q value of bulk acoustic wave resonators is to suppress the transverse shear wave to prevent the occurrence of spurious resonances.
In view of this, in embodiments of the present invention, a support layer is disposed on the piezoelectric layer, a portion of an inner sidewall of the support layer is located at an edge of the active region and is in contact with the second electrode layer, and further, a protection layer is formed on the support layer, and a first cavity is formed between the protection layer and the second electrode layer. In this way, by arranging the support layer and the protective layer at the edge of the active region, the support layer can suppress transverse shear waves (lateral waves) generated when the bulk acoustic wave resonator is excited by an electric field, reduce energy loss of longitudinal waves in the first cavity, and improve the Q value. In addition, compared with the contact area between the supporting layer and the protective layer in the related art, the contact area between the supporting layer and the protective layer in the embodiment of the invention is increased, so that the combination of the supporting layer and the protective layer is firmer, and the reliability of the resonance structure is improved.
Fig. 2 is a schematic cross-sectional view of a bulk acoustic wave resonator structure according to an embodiment of the present invention; referring to fig. 2, the bulk acoustic wave resonant structure includes:
a substrate 201;
a reflective structure 202, a first electrode layer 203, a piezoelectric layer 204, and a second electrode layer 205 stacked in this order on a substrate;
a support layer 206 at least partially over the piezoelectric layer 204, a portion of the inner sidewall of the support layer 206 being at the edge of the active region and in contact with the second electrode layer 205;
a protective layer 207 on the support layer 206; a first cavity is formed between the protection layer 207 and the second electrode layer 205;
the area where the reflection structure 202, the first electrode layer 203, the piezoelectric layer 204, and the second electrode layer 205 overlap in projection along the thickness direction of the substrate is an active area.
In practical applications, the substrate 201 may be composed of Silicon (Si), germanium (Ge) or Silicon-On-Insulator (SOI). The first electrode layer 203 may be referred to as a lower electrode, and correspondingly, the second electrode layer 205 may be referred to as an upper electrode, through which electric energy may be applied to the bulk acoustic wave resonator. The first electrode layer 203 and the second electrode layer 205 may be made of the same material, and specifically may include: a conductive material made of a conductive metal such as aluminum (Al), molybdenum (Mo), ruthenium (Ru), chromium (Cr), iridium (Ir), or platinum (Pt), or an alloy of the conductive metals; preferably, the constituent material of the first electrode layer 203 and the second electrode layer 205 may include molybdenum.
The piezoelectric layer 204 can be used for generating vibration according to inverse piezoelectric characteristics, converting an electrical signal loaded on the first electrode layer 203 and the second electrode layer 205 into an acoustic signal, and converting electrical energy into mechanical energy. In practical applications, the composition material of the piezoelectric layer 204 may include: a material having piezoelectric properties. For example, aluminum nitride, zinc oxide, lithium tantalate, lead zirconate titanate, barium titanate, or the like. The constituent material of the piezoelectric layer may also include a material having piezoelectric properties by doping. The doping can be of a transition metal or a rare metal, for example scandium-doped aluminum nitride or the like.
In practice, the reflective structure 202 comprises a cavity formed between the substrate surface and the first electrode layer 203.
Here, a region where the reflective structure 202, the first electrode layer 203, the piezoelectric layer 204, and the second electrode layer 205 are formed to overlap may be understood as an active region.
The support layer 206 has a thickness. Thus, support layer 206 includes inner and outer sidewalls, it being understood that the inner sidewalls of the support layer are the sidewalls closer to the edge of the active region, while the outer sidewalls of support layer 206 are the sidewalls farther from the edge of the active region.
In practice, the inner sidewall of the support layer 206 is composed of a plurality of parts, and here, a part of the inner sidewall of the support layer 206 can be understood as one part or several parts of the inner sidewall. It should be noted that a part of the inner sidewall of the support layer 206 is close to the edge of the active region, and specifically may be located in the active region or outside the active region. Preferably, a portion of the inner sidewall of the support layer 206 is near the edge of the active region and is located within the active region.
The protective layer 207 can shield and protect an active region formed by the first electrode layer 203, the piezoelectric layer 204 and the second electrode layer 205, so that the influence of a subsequent process in the manufacturing process of the acoustic wave device on a resonance structure is reduced, and the performance of the acoustic wave device is improved.
In practical applications, the material of the protective layer 207 includes glass fiber, epoxy resin, and other composite materials, which have higher tensile strength than compressive strength, and thus are suitable as the protective layer.
In practice, as shown in fig. 2, the Z0 region may include the resonance region of the resonant structure, i.e., the active region; the Z1 region may include a sidewall region of the resonant structure; the Z2 region may include a non-resonant region of the resonant structure. The side wall area is an area where an upper electrode or a lower electrode (or including the upper electrode and the lower electrode) and the piezoelectric layer form an included angle with the substrate surface and project to the substrate surface, the length of the side wall area is L, the projection length of the side wall area on the substrate surface is D, and L is larger than D. The acoustic impedances of the Z0, Z1 and Z2 regions are Z0, Z1 and Z2 respectively, the impedances can be lateral wave impedance or longitudinal wave impedance, but are not limited to the two directions, and the acoustic impedances of the three regions adjacent to each other are not equal to each other.
In practical applications, a part of the inner sidewall of the support layer 206 is located in the sidewall region and contacts the second electrode layer 205;
in some embodiments, support layer 206 comprises: a first support layer 2061 and a second support layer 2062; the material of the first support layer 2061 is the same as or different from that of the second support layer 2062;
wherein the first supporting layer 2061 is located outside the active region, and a part of the first supporting layer 2061 is located on the piezoelectric layer 204, and another part is located on the second electrode layer 205;
a partial region of the second support layer 2062 is positioned on the first support layer 2061, the inner sidewall of the second support layer 2062 is positioned at the edge of the active region and partially contacts the second electrode layer 205; alternatively, a portion of the bottom of the second support layer 2062 is at the edge of the active region and contacts the second electrode layer 205.
In practice, the material of the first support layer 2061 and the material of the second support layer 2062 may be the same or different.
Here, the second support layer 2062 is located on the first support layer 2061, and the top surface of the first support layer 2061 may be flush with the top of the piezoelectric layer 204; or may be flush with the top of the second electrode layer 205.
In practical applications, the inner sidewalls of the first support layer 2061 and the inner sidewalls of the second support layer 2062 may be located at the edge of the active region; and the inner sidewalls of the second support layer 2062 may be located on the second electrode layer 205, as shown by the circular dashed box in fig. 3 a; the inner sidewalls of the second support layer 2062 may also be in contact with the sidewalls of the second electrode layer 205, as shown by the circular dashed box in fig. 3 b. The inner sidewalls of the second support layer 2062 may also be located on the second electrode layer 205 while being in contact with the sidewalls of the second electrode layer 205, as shown by the circular dashed box in fig. 3 c.
It is understood that the first support layer 2061 and the second support layer 2062 may cause the acoustic impedance to change, and further, may suppress the lateral parasitic mode and unnecessary high-order mode of the bulk acoustic wave resonator, and reduce the energy loss; also, the first and second support layers 2061 and 2062 and the protective layer 207 may also serve to protect the active region from being damaged.
Here, the contact area between the second support layer 2062 and the protective layer 207 (as shown in fig. 3 a) is larger than that between the support layer and the protective layer in the related art (as shown in fig. 4, for example), so that the increase of the contact area between the second support layer 2062 and the protective layer 207 can make the bonding between the second support layer 2062 and the protective layer 207 more firm, which is more beneficial to improving the reliability of the resonant structure.
In practical applications, on the premise of ensuring the reliability of the resonant structure, in order to suppress the lateral wave generated when the bulk acoustic wave resonator is excited by the electric field, the embodiments of the present invention provide several different structural arrangements between the first support layer 2061 and the piezoelectric layer 204, and between the second support layer 2062 and the second electrode layer 205.
In some embodiments, a second cavity exists between the inner sidewalls of the first support layer and the bottom of the second support layer and the sidewalls of the piezoelectric layer or the second electrode layer.
In practical applications, as shown in fig. 2 and fig. 3a to fig. 3c, air is present in the second cavity 208, and the resonant wave generated by the active region can be reflected by the air in the second cavity 208, so that at least a part of the lateral wave generated by the piezoelectric layer can be converted into a longitudinal wave, thereby reducing energy loss.
In the natural state, air itself is the best resonant wave reflecting medium.
In other embodiments, the second cavities 208 are filled with a dielectric material that is different from the material of the first support layer 2061 and the second support layer 2062.
In practical applications, as shown in fig. 5, the second cavity 208 may be further filled with a dielectric material; it will be appreciated that the dielectric material may be used to absorb or reflect side waves to reduce energy loss.
Here, the dielectric material filled in the second cavity 208 is different from the materials of the first and second support layers 2061 and 2062.
In practice, the material of the first support layer 2061 and the second support layer 2062 may include a metal material; and the dielectric material filled in the cavity may comprise a material having an absorption or reflection of side waves, for example, silicon dioxide.
In some embodiments, there is no gap between the inner sidewalls of the first support layer and the bottom of the second support layer and the sidewalls of the piezoelectric layer or the second electrode layer; the materials of the first support layer and the second support layer each include a material capable of absorbing or reflecting a lateral wave generated by the piezoelectric layer.
In practical applications, as shown in fig. 6, a solid structure is formed between the inner sidewall of the first support layer 2061 and the sidewall of the piezoelectric layer 204; a solid structure is formed between the inner sidewall of the second support layer 2062 and the sidewall of the second electrode layer 205. Here, the effect of absorbing or reflecting the side waves generated by the piezoelectric layers can be achieved by the materials of the first support layer 2061 and the second support layer 2062.
In some embodiments, the support layer comprises at least M layers of sub-material juxtaposed in a direction perpendicular to the surface of the substrate; the acoustic impedance of two adjacent sub-material layers is different; m is an odd number of not less than 3.
In practice, as shown in fig. 7, each of the first support layer 2061 and the second support layer 2062 may include multiple sub-material layers, each of the multiple sub-material layers may be arranged perpendicular to the surface of the substrate, and the multiple sub-material layers may include the same material; different materials may also be included. Wherein, when the plurality of sub-material layers comprise a plurality of different material layers, the acoustic impedance of two adjacent sub-material layers is different.
In practical applications, each of the first support layer 2061 and the second support layer 2062 includes a first sub-material layer, a second sub-material layer, and a third sub-material layer, which are sequentially arranged in parallel along a direction perpendicular to the substrate 201; the first sub-material layer and the third sub-material layer comprise the same material and both comprise low-acoustic-impedance materials; the second sub-material layer comprises a high acoustic impedance material.
In practice, as shown in FIG. 7, the support layer 206 includes a first sub-material layer 206-1, a second sub-material layer 206-2, and a third sub-material layer 206-3; here, the first sub-material layer 206-1 and the third sub-material layer 206-3 may include a low acoustic impedance material; the second sub-material layer 206-2 may comprise a high acoustic impedance material; alternatively, the first sub-material layer 206-1 and the third sub-material layer 206-3 may comprise high acoustic impedance materials; the second sub-material layer 206-2 may comprise a low acoustic impedance material.
In practice, the high acoustic impedance material may comprise aluminum nitride (AlN), tungsten (W), titanium Tungsten (TiW), silicon nitride (Si)3N4) And molybdenum (Mo), etc.; the low acoustic impedance material may comprise silicon dioxide (SiO)2) Silicon oxycarbide (SiOC), benzocyclobutene (BCB), and polymers, among others.
It should be noted that fig. 5, fig. 6, and fig. 7 each only show one of three connection manners of the partial inner side wall of the support layer 206 and the second electrode layer 205 (contact with the second electrode layer, on the second electrode layer 205, and both contact with the second electrode layer and on the second electrode layer 205), and it is understood that the schemes shown in fig. 5, fig. 6, and fig. 7 are also applicable to the other two connection manners.
In practice, the thicknesses of first sub-material layer 206-1, second sub-material layer 206-2, and third sub-material layer 206-3 each include 1/4 times the wavelength of the lateral wave generated by piezoelectric layer 204.
Here, the 1/4 wavelength of each material layer set as the incident wave (the lateral wave generated by the piezoelectric layer) can create a highly efficient mirror that reflects the incident wave, so that part of the lateral wave generated by the piezoelectric layer 204 can be converted into a longitudinal wave and reflected back to the resonant structure, thereby achieving a reduction in energy loss.
It should be noted that air is the best resonant wave reflecting medium compared to the commonly filled solid dielectric material.
In some embodiments, the first support layer is a complete annular structure;
alternatively, the first and second electrodes may be,
the first support layer exists in a multi-stage discontinuous structure formed in a shape surrounding the second electrode layer.
In practice, the first support layer 2061 is a complete ring-shaped structure, as shown in FIG. 9 a; alternatively, the first support layer 2061 may have a discontinuous multi-segment structure, and as shown in fig. 8, the multi-segment discontinuous structure formed in a shape surrounding the second electrode layer exists in the top view shown in fig. 8.
It is understood that the first support layer 2061 has a complete ring structure, which reduces the loss caused by the side waves and is more favorable for reducing the parasitic resonance, compared with the discontinuous structure of the first support layer 2061.
In some embodiments, the support layer 206 is not connected to the first electrode layer 203.
Here, the support layer 206 is connected to the second electrode layer 205, but not to the first electrode layer 203.
In some embodiments, the material of the support layer 206 comprises a conductive material or a non-conductive material.
In practice, the material of the support layer 206 may include a conductive material, such as a metal; the material of the support layer 206 may also include a non-conductive material, such as silicon dioxide.
It is understood that when the material of the support layer 206 includes a conductive material, and the contact area between the second support layer 2062 and the protection layer 207 (as shown in fig. 3 a) is larger than that in the related art (as shown in fig. 4, for example), the contact area between the second support layer 2062 and the protection layer 207 is increased, so that the heat dissipation area can be increased, and good heat dissipation of the resonant structure can be ensured.
In some embodiments, the resonant structure further comprises an etch hole;
etching holes through the piezoelectric layer and in the discontinuous support layer (as shown in fig. 8); one end of the etching hole is communicated with the reflecting structure, and the other end of the etching hole is communicated with the second cavity;
or, the etching holes include a first etching hole and a second etching hole (as shown in fig. 11 i), the first etching hole penetrates through the piezoelectric layer and is located at the outer side of the support layer, and the second etching hole penetrates through the second support layer and is located on the second cavity;
or the second etching hole is arranged on part of the first supporting layer;
alternatively, the second etching hole is under the support layer.
When the support layer is a continuous structure, the etching holes may be located outside the first support layer 2061 as shown in fig. 9b and 9 c; in some embodiments, the etch holes may also be located outside the second support layer 2062. The etching hole may include one or more.
It should be noted that fig. 9a is a schematic top view of a resonant structure provided by the embodiment of the present invention, fig. 9b shows a schematic cross-sectional view at a position BB 'of fig. 9a, and fig. 9c shows a schematic cross-sectional view at a position AA' of fig. 9 a; in fig. 9a, the second supporting layer and the passivation layer are not shown for clarity of the etching hole position.
In practice, as shown in FIG. 9b, the etching holes are connected to the reflective structure 202, so that the etching gas or liquid can etch the sacrificial layer in the reflective structure 202 through the etching holes.
Here, when the reflective structure 202 is filled with a sacrificial layer, the sacrificial layer serves to support the first electrode layer 203 formed in a subsequent process support.
It should be noted that, in the subsequent process, the second supporting layer 2062 is formed, a gap exists between the inner sidewall of the second supporting layer 2062 and the inner wall of the second electrode layer 205, and when the gap is filled with a sacrificial layer, the second supporting layer 2062 is disposed on the sacrificial layer.
It should be noted that the etching holes shown in fig. 9b are not labeled in other figures. Compared to fig. 9b, fig. 9c shows a cross-sectional view of the connection structure of the first support layer and the second support layer in another direction, which has been described above and will not be described herein again.
In the embodiment of the invention, the support layer is arranged on the piezoelectric layer, part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer, in addition, the protective layer is formed on the support layer, and a first cavity is formed between the protective layer and the second electrode layer. In this way, by arranging the support layer and the protective layer at the edge of the active region, the support layer can suppress transverse shear waves (lateral waves) generated when the bulk acoustic wave resonator is excited by an electric field, and reduce the loss of longitudinal waves in the active region in terms of energy, thereby improving the Q value. In addition, compared with the contact area between the supporting layer and the protective layer in the related art, the contact area between the supporting layer and the protective layer in the embodiment of the invention is increased, so that the combination of the supporting layer and the protective layer is firmer, and the reliability of the resonance structure is improved.
Based on the bulk acoustic wave resonant structure, an embodiment of the present invention further provides a filter, including: the embodiment of the invention provides a bulk acoustic wave resonance structure.
In practical applications, the filter generally includes a plurality of resonant structures, and the plurality of resonant structures are connected by way of Ladder cascade (english may be expressed as Ladder Type).
Based on the bulk acoustic wave resonant structure, an embodiment of the present invention further provides a method for manufacturing a bulk acoustic wave resonant structure, as shown in fig. 10, the method includes the following steps:
step 1001: sequentially forming a reflecting structure 202, a first electrode layer 203, a piezoelectric layer 204 and a second electrode layer 205 which are stacked on a substrate 201;
step 1002: forming at least a portion of a support layer 206 over the piezoelectric layer 204; wherein part of the inner side wall of the support layer 206 is at the edge of the active region and contacts with the second electrode layer 205;
step 1003: forming a protective layer 207 on the support layer 206; a first cavity is formed between the protection layer 207 and the second electrode layer 205;
the area where the reflection structure 202, the first electrode layer 203, the piezoelectric layer 204, and the second electrode layer 205 overlap in projection along the thickness direction of the substrate 201 is an active area.
Here, in step 1001, the manufacturing methods of the reflective structure 202, the first electrode layer 203, the piezoelectric layer 204, and the second electrode layer 205 are well known in the related art, and are not described herein again, and the corresponding structures formed according to the corresponding methods are shown in fig. 11a and 11 b.
It should be noted that fig. 11a is a schematic top view of the resonant structure provided in the embodiment of the present invention, fig. 11b is a schematic cross-sectional view at the position AA 'of fig. 11a, and it can be understood that the dashed frame portion in fig. 11b only corresponds to the position AA' of the top view of fig. 11 a.
The following focuses on the manner in which the support layer 206 is formed. For clarity of description, the formation of the resonant structure with the second cavity 208 (refer to fig. 3a to 3c) is taken as an example for illustration.
It should be noted that, in practical applications, the structure of the support layer 206 can be obtained in various ways. The first mode is described below:
in step 1002, primarily support layer 206 is formed.
In some embodiments, support layer 206 comprises a first support layer 2061 and a second support layer 2062; the material of the first support layer 2061 is the same as or different from that of the second support layer 2062;
forming at least a portion of a support layer over the piezoelectric layer 204, including:
forming a first support layer 2061 on the piezoelectric layer 204; the first support layer 2061 is outside the active region, and a portion of the first support layer 2061 is located on the piezoelectric layer 204, and another portion is located on the second electrode layer 205;
after the first support layer 2061 is formed, a second support layer 2062 is formed on the first support layer 2061; the second support layer 2062 is partially in contact with the first support layer 2061, the inner sidewalls of the second support layer 2062 are at the edge of the active region and partially contact the second electrode layer 205; alternatively, a portion of the bottom of the second support layer 2062 is at the edge of the active region and contacts the second electrode layer 205.
In practice, the second support layer 2062 is disposed on the first support layer 2061, and the bottom of the second support layer 2062 may be in full contact with the first support layer 2061 or in partial contact with the first support layer 2061.
In some embodiments, a first support layer 2061 is formed on the piezoelectric layer 204 and the second electrode layer 205 outside the active region, and a second support layer 2062 is formed on the edge of the active region and the first support layer 2061.
Illustratively, as shown in fig. 11c, a portion of the first support layer 2061 is formed on the piezoelectric layer 204 and another portion of the first support layer 2061 is formed on the region Z2 of the second electrode layer 205.
Forming at least a portion of a support layer 206 on the piezoelectric layer 204 includes:
a first support layer 2061 having a top surface flush with the top surface of the second electrode layer 205 or the top surface of the piezoelectric layer 204 is formed on the piezoelectric layer 204. Here, only one case where the top surface of the first support layer 2061 is flush with the top surface of the second electrode layer 205 is shown in fig. 11 c.
In some embodiments, forming the first support layer 2061 on the piezoelectric layer outside the active region and the second electrode layer 205 includes:
forming a first support layer 2061 having a top surface flush with a top surface of the second electrode layer 205 of the active region on the piezoelectric layer 204 and the second electrode layer 205;
forming a second support layer 2062 having a top surface higher than that of the second electrode layer 205 on the first support layer 2061; the inner side walls of the second support layer 2062 contact the second electrode layer 205.
In some embodiments, as shown in fig. 11d, the method further comprises:
before forming the second support layer 2062, a first sacrificial layer 210 is formed on the piezoelectric layer 204 and on one side of the inner side wall corresponding to the first support layer 2061 on the piezoelectric layer 204;
a portion of the second support layer 2062 having a top surface higher than the top surface of the second electrode layer 205 is formed on a portion of the first support layer 2061 and the first sacrificial layer 210.
In a subsequent process, the first sacrificial layer 210 is removed, and a second cavity 208 may be formed between the first support layer 2061 and the piezoelectric layer 204.
The method further comprises the following steps:
forming a second support layer 2062 having a top surface higher than that of the second electrode layer 205 on the first support layer 2061 and the first sacrificial layer 210;
after removing the first sacrificial layer 210, a second cavity 208 is formed between the second support layer 2062 and the second electrode layer 205.
Note that, as shown in fig. 11d, before the second support layer 2062 is formed, a first sacrificial layer 210 flush with the top surface of the piezoelectric layer 204 is formed between the first support layer 2061 and the piezoelectric layer 204; and simultaneously forming a first sacrificial layer 210 between the first support layer 2061 and the second electrode layer 205, which is flush with the top surface of the second electrode layer 205.
Next, as shown in fig. 11e and 11f, a second support layer 2062 is formed on the first support layer 2061, the first sacrificial layer 210, and the second electrode layer 205.
Here, fig. 11e is a schematic top view of the resonant structure provided by the embodiment of the present invention, and fig. 11f is a schematic cross-sectional view at AA' of fig. 11 e.
Note that the second support layer 2062 may be formed on the second electrode layer 205; or may be in contact with the sidewalls of the second electrode layer 205; or may be both on the second electrode layer 205 and in contact with the sidewalls of the second electrode layer 205. Fig. 11e and 11f show only the second electrode layer 205.
It should be noted that the region Z2 of the second electrode layer 205 can be understood as a lead portion in the second electrode layer 205 for electrically connecting with an external device, and is located outside the active region.
In practical applications, the first support layer 2061 and the second support layer 2062 may be formed by a thin film growth and etching process, which has been mentioned above and will not be described herein again. Thus, the structures of fig. 11e and 11f can be obtained by the above-described process.
It should be noted that, in the practical operation of the above embodiment, in order to improve the process operability, a portion of the first support layer 2061 on the piezoelectric layer 204 and another portion of the first support layer 2061 on the second electrode layer 205 are formed simultaneously.
Note that, the removing manner of the first sacrificial layer 210 will be described in a subsequent process.
Next, as shown in fig. 11g and 11h, etching holes (first etching holes) penetrating the piezoelectric layer 204, the first sacrificial layer 210, and the third sacrificial layer are formed on the substrate 201.
Fig. 11g is a schematic top view of the resonant structure according to the embodiment of the present invention, and fig. 11h is a schematic cross-sectional view at the position BB' of fig. 11 g.
In practical application, the method further comprises: before the support layer is formed, an etch hole is formed through the piezoelectric layer 204, then the first sacrificial layer 210 is formed and communicated with the third sacrificial layer of the reflective structure through the etch hole, and then the support layer is formed.
In some embodiments, as shown in fig. 11i, the second support layer above the first sacrificial layer 210 forms a second etching hole, and the first sacrificial layer and the third sacrificial layer can be removed through the first etching hole and the second etching hole at the same time to form a cavity.
It is to be understood that the etching hole may be located in the support layer 206 such that the support layer 206 exists in a multi-segment discontinuous structure formed in a shape surrounding the second electrode layer; or outside the support layer 206, so that the support layer 206 forms a complete ring structure, i.e. a closed ring-shaped three-dimensional structure.
Next, as shown in fig. 11j, the first sacrificial layer and the third sacrificial layer above the substrate are etched and removed through the etching holes, and after the first sacrificial layer and the third sacrificial layer are removed, the second cavity 208 and the reflective structure 202 are formed.
In practical applications, the composition materials of the first sacrificial layer and the third sacrificial layer may include: phosphosilicate glass (PSG), silicon dioxide, or the like. For example, silicon dioxide is the material of the sacrificial layer, Silane (SiH) can be used4) With oxygen (O)2) As a reaction gas, a sacrificial layer is formed on a surface of a substrate by a chemical vapor deposition process.
In practical applications, the sacrificial layer may be removed by using a dry etching process or a wet etching process. Illustratively, the dry Etching may be specifically Vapor Etching (Vapor Etching), and the Etching gas includes an Etching gas that can be used to etch the material of the sacrificial layer, and more specifically, when the material of the sacrificial layer includes silicon dioxide, the Etching gas may be HF or the like.
In some embodiments, the method further comprises:
after forming the second electrode layer 205, an adjustment layer is formed over the second electrode layer 205;
the thickness of the tuning layer is trimmed to tune the frequency of the resonant structure before forming the protective layer 207.
It is understood that the adjustment of the resonant structure frequency can be achieved by adjusting the thickness of the first electrode Layer 203, the second electrode Layer 205 or the piezoelectric Layer 204, and in practical applications, after the second electrode Layer is formed, an adjustment Layer (which may be expressed as Trimming Layer) is formed on the second electrode Layer 205. The frequency of the resonant structure is adjusted by changing the thickness of the adjustment layer.
In practice, adjusting the thickness of the adjustment layer includes increasing the thickness of the adjustment layer and decreasing the thickness of the adjustment layer. In specific implementation, the increase of the thickness of the adjusting layer can be completed by a yellow light exposure and development process and a deposition process; the thickness of the adjusting layer can be reduced by a yellow light exposure and development process and an etching process; more specifically, the method of trimming the adjustment layer may include inductively Coupled Plasma etching (ICP), and it is understood that the method of trimming the adjustment layer is not limited thereto.
Next, in step 1003, mainly the protective layer 207 is formed.
As shown in fig. 11k, a protective layer 207 is formed on the support layer 206; a first cavity is formed between the protection layer 207 and the second electrode layer 205. Here, the first cavity may be understood as a resonant cavity.
In practical applications, the protective layer 207 may be formed by applying a metal, a ceramic, an organic material, or the like on the support layer. If the material of the protection layer 207 is a dry film photoresist material, a layer of the dry film photoresist material may be applied on the top surface of the support layer by an application process, and then the dry film photoresist material at a position other than the desired position is removed by an exposure and development process, so as to form the protection layer 207.
It is understood that the air in the first cavity can reflect longitudinal waves generated by the piezoelectric layer 204. Moreover, when the resonant structure is under compressive or tensile force, the protective layer 207 can be used to bear external compressive and tensile stress, so that the protective layer 207 can enhance the strength of the entire resonant structure and improve the performance failure problem of the device caused by external force.
The above embodiments have been described mainly with respect to the manner of manufacturing the resonant structure having the cavity.
It is understood that, for the resonant structure (refer to fig. 5) with the dielectric material in the cavity of the foregoing embodiment, the manufacturing method may be that, in the manufacturing method of the foregoing embodiment, when the first sacrificial layer is formed, the material of the first sacrificial layer is replaced with the dielectric material, and in a subsequent process, the dielectric material is not removed, so that the resonant structure with the filled dielectric material may be formed.
In practical applications, for the resonant structure without a cavity in the support layer (refer to fig. 6) of the foregoing embodiments, the support layer 206 may be formed at one time, and the material for forming the support layer 206 may include a material capable of absorbing or reflecting the lateral wave generated by the piezoelectric layer. In practical applications, for the resonant structure of the foregoing embodiment in which the supporting layer includes multiple sub-material layers (refer to fig. 7), the manufacturing method may be:
in some embodiments, forming at least a portion of the support layer 206 over the piezoelectric layer 204 comprises:
sequentially forming a first sub-material layer 206-1, a second sub-material layer 206-2 and a third sub-material layer 206-3 which are arranged in parallel along the direction vertical to the substrate 201 on the piezoelectric layer 204; wherein the first sub-material layer and the third sub-material layer are formed simultaneously;
the first sub-material layer and the third sub-material layer comprise the same material and both comprise low-acoustic-impedance materials; the second sub-material layer comprises a high acoustic impedance material.
In practice, a first sub-material layer 206-1, a second sub-material layer 206-2, and a third sub-material layer 206-3 are sequentially formed over the piezoelectric layer 204 to form the first support layer 2061.
At the same time, a first sub-material layer 206-1, a second sub-material layer 206-2 and a third sub-material layer 206-3 are formed over the second electrode layer 205 to form a second support layer 2062.
It should be noted that, in practical applications, the structure of the support layer 206 may also be obtained in another way. The second mode is described below:
in some embodiments, as shown in fig. 12a, support layer 206 comprises: a first support layer 2061 and a second support layer 2062; the material of the first support layer 2061 is the same as or different from that of the second support layer 2062;
forming at least a portion of a support layer 206 over the piezoelectric layer 204, comprising:
forming a first support layer 2061 and a portion of a second support layer 2062 on the piezoelectric layer 204; the projections of the first support layer 2061 and a portion of the second support layer 2062 on a plane parallel to the substrate surface overlap;
the first support layer 2061 is outside the active region, and a portion of the first support layer 2061 is on the piezoelectric layer and another portion is on the second electrode layer 205; the top surface of the first support layer 2061 is flush with the top surface of the second electrode layer 205 of the active region;
a portion of the second support layer 2062 is located on the first support layer 2061; a portion of the top surface of the second support layer 2062 is higher than the top surface of the second electrode layer 205 of the active region.
In some embodiments, the method further comprises:
as shown in fig. 12b, after forming the first support layer 2061 and a portion of the second support layer 2062, a second sacrificial layer 211 is formed on the piezoelectric layer 204 and the second electrode layer 205; the top surface of the second sacrificial layer 211 is flush with the top surface of the second electrode layer 205 of the active region;
as shown in fig. 12c, another portion of the second support layer 2062 is formed on the top surface of the second sacrificial layer 211; another portion of the inner sidewalls of the second support layer 2062 is at the edge of the active region and partially contacts the second electrode layer 205; alternatively, a part of the bottom of another part of the second support layer 2062 is at the edge of the active region and contacts the second electrode layer 205;
as shown in fig. 12d, the second sacrificial layer 211 is removed to form a second cavity 208 between the first and second support layers 2061 and 2062 and the piezoelectric layer 204.
It should be noted that the second sacrificial layer 211 is made of the same material in different forming methods as the first sacrificial layer 210 in the previous embodiment.
In practical application, a material layer can be formed through a film growth process; then, the material layer is etched by photolithography and etching processes to remove an excess portion, so as to form a first support layer 2061 and a second support layer 2062 on the piezoelectric layer 204 and the second electrode layer 205. If the support layer 206 is a dry film photoresist material, the dry film photoresist material can be removed at other positions than the desired position by exposure and development processes.
Here, the thin film growth process may include, but is not limited to, evaporation, sputtering, and the like.
It should be noted that, in practical applications, the structure of the support layer 206 may also be obtained in another way. The third mode is described below:
in some embodiments, as shown in fig. 13a to 13f, the method further comprises:
forming etching holes penetrating the piezoelectric layer 204 and communicating with the reflective structure 202 on the outer side of the support layer 206 before forming at least part of the support layer 206 on the piezoelectric layer 204;
as shown in fig. 13b, sacrificial material is deposited in the etch holes and on the piezoelectric layer 204, the second electrode layer 205;
as shown in fig. 13c, the sacrificial material covering the top surfaces of the piezoelectric layer 204 and the second electrode layer 205 and part of the sacrificial material covering the piezoelectric layer 204 and the second electrode layer 205 are removed, and the sacrificial layer near the etching holes and the sidewalls are remained to form a fourth sacrificial layer; a process such as Chemical-Mechanical Planarization (CMP) Planarization is used.
Forming at least part of a support layer 206 over the piezoelectric layer 204 and the second electrode layer 205 comprises:
as shown in fig. 13d, a support material is deposited on the exposed surface of the piezoelectric layer 204, the top surface of the second electrode layer 205 and the fourth sacrificial layer;
as shown in fig. 13e, removing a portion of the support material on the piezoelectric layer 204 and the second electrode layer 205 of the active region to form a support layer 206;
the method further comprises the following steps:
as shown in fig. 13f, the fourth sacrificial layer is removed.
In practical applications, the sacrificial material between the substrate 201 and the first electrode layer 203 and in the etching holes is removed at the same time as the fourth sacrificial layer is removed.
It should be noted that, in practical applications, the structure of the support layer 206 may also be obtained in another way. The fourth mode is described below:
in some embodiments, support layer 206 comprises: a first support layer 2061 and a second support layer 2062; the material of the first support layer 2061 is the same as or different from that of the second support layer 2062;
forming at least a portion of a support layer 206 over the piezoelectric layer 204, comprising:
as shown in fig. 14a, a first portion 2061a of the first support layer is formed on the piezoelectric layer 204; the first portion 2061a of the first support layer is outside the active region and the top surface of the first portion 2061a of the first support layer is flush with the top surface of the piezoelectric layer 204 of the active region.
Next, as shown in fig. 14b, after forming the first portion 2061a of the first support layer, a second portion 2061b of the first support layer is formed on the first portion 2061a of the partial first support layer; wherein the top surface of the second portion 2061b of the first support layer is flush with the top surface of the second electrode layer 205 of the active region.
Next, as shown in fig. 14c, a sacrificial material is deposited on the piezoelectric layer 204, the second portion 2061b of the first support layer, the second electrode layer 205 of the active region, and the first portion 2061a of a portion of the first support layer.
Next, as shown in fig. 14d, a part of the sacrificial material is removed to form a fifth sacrificial layer; wherein the top surface of the fifth sacrificial layer is flush with the top surface of the second electrode layer 205 of the active region. Processes such as chemical mechanical planarization and planarization are used.
Next, as shown in fig. 14e, a second support layer 2062 is formed on the second portion 2061b of the first support layer, the fifth sacrificial layer, and the second electrode layer 205 of the active region; the second support layer 2062 is partially in contact with the second portion 2061b of the first support layer, the inner sidewalls of the second support layer 2062 are at the edge of the active region and partially contact the second electrode layer 205; alternatively, a portion of the bottom of the second support layer 2062 is at the edge of the active region and contacts the second electrode layer 205.
Next, as shown in fig. 14f, the fifth sacrificial layer and the third sacrificial layer are simultaneously removed.
Note that after the fifth sacrificial layer is removed, an etching hole is formed in a part of the first support layer 2061. The etch hole communicates with the second cavity 208.
In addition, it should be noted that the thickness of the partial adjustment layer is reduced by removing the material of the partial adjustment layer; thus, low-frequency lateral wave generated by the piezoelectric layer is favorably moved to high frequency; in practical applications, the variation of the thickness of the adjustment layer can be formed in various ways, three of which are described below;
the first method is as follows:
as shown in fig. 15a, the second electrode layer 205 in the active region is trimmed; wherein the change in the thickness of the adjustment layer is achieved by reducing the thickness of the second electrode layer 205.
The second method comprises the following steps:
as shown in fig. 15b, before forming the second support layer 2062, an adjustment layer is formed on the second electrode layer 205 in the active region;
next, a second support layer 2062 is formed on the adjustment layer;
next, after the second support layer 2062 is formed, the adjustment layer is trimmed to effect a change in the thickness of the adjustment layer.
The third method comprises the following steps:
as shown in fig. 15c, after forming a second support layer 2062 on the second electrode layer 205, an adjustment layer is formed on the second electrode layer 205 of the active region and between the second support layers 2062;
in the above embodiments, the thickness of the adjustment layer is changed by trimming the adjustment layer, so as to adjust the frequency of the resonant structure.
In some embodiments, the method further comprises:
forming a first sacrificial layer on the piezoelectric layer and the second electrode layer after forming the first support layer; the top surface of the first sacrificial layer is flush with the top surface of the adjusting layer;
forming a second supporting layer on the top surface of the first sacrificial layer;
the first sacrificial layer is removed to form a second cavity between the first and second support layers and the piezoelectric layer.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus, system, and method may be implemented in other ways. The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (19)
1. A bulk acoustic wave resonant structure, comprising:
a substrate;
the reflecting structure, the first electrode layer, the piezoelectric layer and the second electrode layer are sequentially stacked on the substrate;
a support layer at least partially located above the piezoelectric layer, wherein part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer;
a protective layer on the support layer; a first cavity is formed between the protective layer and the second electrode layer;
and the projection overlapping area of the reflecting structure, the first electrode layer, the piezoelectric layer and the second electrode layer along the thickness direction of the substrate is an active area.
2. The resonant structure of claim 1, wherein the support layer comprises: a first support layer and a second support layer; wherein the content of the first and second substances,
the first support layer is positioned outside the active region, part of the first support layer is positioned on the piezoelectric layer, and the other part of the first support layer is positioned on the second electrode layer;
a partial area of the second support layer is positioned on the first support layer, and the inner side wall of the second support layer is positioned at the edge of the active area and partially contacts the second electrode layer; or part of the bottom of the second support layer is positioned at the edge of the active region and contacts the second electrode layer;
the material of the first support layer is the same as or different from that of the second support layer.
3. The resonant structure according to claim 2, wherein a second cavity is present between the inner side wall of the first support layer and the bottom of the second support layer and the side wall of the piezoelectric layer or the second electrode layer.
4. The resonant structure according to claim 3, wherein the second cavity is filled with a dielectric material different from the materials of the first and second support layers.
5. The resonant structure according to claim 2, wherein there is no gap between the inner sidewalls of the first support layer and the bottom of the second support layer and the sidewalls of the piezoelectric layer or the second electrode layer; the materials of the first and second support layers each comprise a material capable of absorbing or reflecting lateral waves generated by the piezoelectric layer.
6. The resonant structure according to claim 1, characterized in that the support layer comprises at least M layers of sub-material juxtaposed in a direction perpendicular to the substrate surface; the acoustic impedance of two adjacent sub-material layers is different; m is an odd number more than or equal to 3.
7. The resonant structure of claim 2, wherein the first support layer is a complete ring-shaped structure;
alternatively, the first and second electrodes may be,
the first support layer exists in a multi-segment discontinuous structure formed in a shape surrounding the second electrode layer.
8. The resonant structure of claim 7, further comprising an etch hole;
the etching hole penetrates through the piezoelectric layer and is positioned in the discontinuous supporting layer; one end of the etching hole is communicated with the reflecting structure, and the other end of the etching hole is communicated with the second cavity;
or, the etching holes comprise a first etching hole and a second etching hole, the first etching hole penetrates through the piezoelectric layer and is positioned at the outer side of the supporting layer, and the second etching hole penetrates through the second supporting layer and is positioned on the second cavity; or the second etching hole is arranged on part of the first supporting layer; or the second etching hole is arranged below the support layer.
9. The resonant structure according to claim 1, wherein the material of the support layer comprises a conductive material or a non-conductive material.
10. A method of fabricating a bulk acoustic wave resonant structure, comprising:
sequentially forming a reflecting structure, a first electrode layer, a piezoelectric layer and a second electrode layer which are stacked on a substrate;
forming at least a portion of a support layer over the piezoelectric layer; wherein part of the inner side wall of the support layer is positioned at the edge of the active region and is in contact with the second electrode layer;
forming a protective layer on the support layer; a first cavity is formed between the protective layer and the second electrode layer;
and the area where the reflection structure, the first electrode layer, the piezoelectric layer and the second electrode layer are projected and overlapped along the thickness direction of the substrate is an active area.
11. The method of claim 10, wherein the support layer comprises: a first support layer and a second support layer; the material of the first supporting layer is the same as or different from that of the second supporting layer;
said forming at least a portion of a support layer over said piezoelectric layer comprising:
forming the first support layer on the piezoelectric layer; the first support layer is positioned outside the active region, part of the first support layer is positioned on the piezoelectric layer, and the other part of the first support layer is positioned on the second electrode layer;
forming the second support layer on the first support layer after forming the first support layer; the second support layer is partially contacted with the first support layer, the inner side wall of the second support layer is positioned at the edge of the active region and partially contacted with the second electrode layer; or part of the bottom of the second support layer is positioned at the edge of the active region and contacts the second electrode layer.
12. The method of claim 11,
the forming the first support layer on the piezoelectric layer and the second electrode layer outside the active region includes:
forming the first support layer with a top surface flush with a top surface of the second electrode layer of the active region on the piezoelectric layer and the second electrode layer;
forming the second support layer having a top surface higher than a top surface of the second electrode layer on the first support layer; the inner side wall of the second support layer is in contact with the second electrode layer.
13. The method of claim 12, further comprising:
forming a first sacrificial layer on the piezoelectric layer and the second electrode layer and on one side of an inner sidewall of the first support layer before forming the second support layer; the first sacrificial layer is flush with the top surface of the second electrode layer of the active region;
forming the second support layer on the edge of the second electrode layer of the active region and the first sacrificial layer;
the top surface of the second supporting layer is higher than the top surfaces of the second electrode layer of the active region and the first sacrificial layer;
and removing the first sacrificial layer to form a second cavity between the bottom of the first and second support layers and the piezoelectric layer.
14. The method of claim 10, further comprising:
before forming at least part of the support layer on the piezoelectric layer, forming etching holes which penetrate through the piezoelectric layer and are communicated with the reflecting structure on the outer side of the support layer;
depositing sacrificial materials in the etching holes and on the piezoelectric layer and the second electrode layer;
removing the sacrificial material covering the top surfaces of the piezoelectric layer and the second electrode layer and part of the sacrificial material covering the piezoelectric layer and the second electrode layer, and reserving the sacrificial layer near the etching holes and on the side wall to form a fourth sacrificial layer;
forming at least a portion of a support layer over the piezoelectric layer and the second electrode layer, comprising:
depositing a support material on the surface of the exposed piezoelectric layer, the top surface of the second electrode layer and the fourth sacrificial layer;
removing a portion of the support material on the piezoelectric layer and the second electrode layer of the active region to form a support layer;
the method further comprises the following steps:
and removing the fourth sacrificial layer.
15. The method of claim 10, further comprising:
before forming the support layer on the piezoelectric layer, forming a first etching hole which penetrates through the piezoelectric layer and is communicated with the reflecting structure on the outer side of the support layer;
forming a first portion of a first support layer over the piezoelectric layer and a second portion of the first support layer in a region other than the vicinity of the first etch hole;
the top surface of the first part of the first support layer is flush with the top surface of the piezoelectric layer of the active area; the top surface of the second part of the first support layer is flush with the top surface of the second electrode layer of the active region;
after depositing a fifth sacrificial layer on the piezoelectric layer, the support layer, the first etching holes and the second electrode layer, grinding the top surfaces of the support layer and the second electrode layer covering the active region;
forming a second supporting layer on the second part of the first supporting layer and a fifth sacrificial layer covering the first part, wherein the sacrificial layer between the second supporting layer and the first part of the first supporting layer becomes a second etching hole;
and removing the fifth sacrificial layer and the sacrificial layer of the reflective structure through the first etching hole and the second etching hole.
16. The method of claim 13, further comprising:
before forming the support layer on the piezoelectric layer, forming a first etching hole which penetrates through the piezoelectric layer and is communicated with the reflecting structure on the outer side of the support layer;
forming a third etching hole penetrating through the second support layer on the first sacrificial layer;
and removing the first sacrificial layer and the sacrificial layer of the reflecting structure through the first etching hole and the third etching hole.
17. The method of claim 10,
said forming at least a portion of a support layer over said piezoelectric layer comprising:
forming a first sub-material layer, a second sub-material layer and a third sub-material layer which are arranged in parallel along a direction vertical to the substrate on the piezoelectric layer; wherein the first sub-material layer and the third sub-material layer are formed simultaneously;
the first sub-material layer and the third sub-material layer comprise the same material and both comprise low-acoustic-impedance materials; the second sub-material layer comprises a high acoustic impedance material.
18. The method of claim 11, further comprising:
forming an adjustment layer on the second electrode layer after forming the second electrode layer;
before forming the protective layer, the thickness of the adjustment layer is trimmed to adjust the frequency of the resonant structure.
19. The method of claim 18, further comprising:
forming a first sacrificial layer on the piezoelectric layer and the second electrode layer after forming the first support layer; the top surface of the first sacrificial layer is flush with the top surface of the adjusting layer;
forming the second support layer atop the first sacrificial layer;
removing the first sacrificial layer to form a second cavity between the first and second support layers and the piezoelectric layer.
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